Updating Mongo documents through node but no results - node.js

Question

I've been trying to add emails (which is a new field) to my "people" collection but I don't know why I'm getting no results from the server. This is my code
for (key in D_emails) {
console.log(D_emails[key])
try {
o_id = new mongo.ObjectID(D_emails[key])
collection.updateOne({
_id: o_id
}, {
$set: {
"Email": key
}
}, function(err, results) {
if (err) {
throw err
} else if (results.length) {
console.log(results)
} else {
console.log("no results")
}
});
} catch (e) {
print(e);
}
}

Answer 1

According to mongo documentation for updateOne the response of the query (results in your case) does not contain length element and it is not an array or an object. This will be the response according to the documentation:
Returns a document containing:
A boolean acknowledged as true if the operation ran with write concern or false if write concern was disabled
matchedCount containing the number of matched documents
modifiedCount the number of modified documents upsertedId containing the _id for
the upserted document

Answer 2

first of all. try to code without try catch blocks when using the concept of "err" object being returned from every asynchronous callback. You can treat the error right inside the callback. "throwing" the error will also prevent other emails from being updated. But maybe that's what you want. It doesn't really matter now.
Now, back to your question. let me show you what result is, in this example:
// inserting.
collection.insertOne({_id: "lala", a:10, b:20}, function (err, r) {
assert.equal(null, err);
assert.equal(1, r.insertedCount);
// updating.
collection.updateOne({_id: "lala"}, {$set: {a: 99}}, {}, function(err, result) {
assert.equal(null, err);
console.log(result) // first thing printed.
console.log(JSON.stringify(result, null, "\t")) // second print.
// checking whats inside it.
collection.findOne({_id: "lala"}, {}, function(err, doc) {
assert.equal(null, err);
console.log(doc) // third print.
db.close() // don't close connection if you don't need to.
})
})
})
the 3 printed things will be (scroll to the end to see what you actually want):
CommandResult {
result: { ok: 1, nModified: 1, n: 1 },
connection:
Connection {
domain: null,
_events:
{ close: [Object],
error: [Object],
timeout: [Object],
parseError: [Object],
connect: [Function] },
_eventsCount: 5,
_maxListeners: undefined,
options:
{ socketOptions: {},
auto_reconnect: true,
host: 'localhost',
port: 27017,
cursorFactory: [Object],
reconnect: true,
emitError: true,
size: 5,
disconnectHandler: [Object],
bson: BSON {},
messageHandler: [Function],
wireProtocolHandler: [Object] },
id: 1,
logger: Logger { className: 'Connection' },
bson: BSON {},
tag: undefined,
messageHandler: [Function],
maxBsonMessageSize: 67108864,
port: 27017,
host: 'localhost',
keepAlive: true,
keepAliveInitialDelay: 0,
noDelay: true,
connectionTimeout: 0,
socketTimeout: 0,
destroyed: false,
domainSocket: false,
singleBufferSerializtion: true,
serializationFunction: 'toBinUnified',
ca: null,
cert: null,
key: null,
passphrase: null,
ssl: false,
rejectUnauthorized: false,
checkServerIdentity: true,
responseOptions: { promoteLongs: true },
flushing: false,
queue: [],
connection:
Socket {
connecting: false,
_hadError: false,
_handle: [Object],
_parent: null,
_host: 'localhost',
_readableState: [Object],
readable: true,
domain: null,
_events: [Object],
_eventsCount: 8,
_maxListeners: undefined,
_writableState: [Object],
writable: true,
allowHalfOpen: false,
destroyed: false,
_bytesDispatched: 334,
_sockname: null,
_pendingData: null,
_pendingEncoding: '',
server: null,
_server: null,
_idleNext: null,
_idlePrev: null,
_idleTimeout: -1,
read: [Function],
_consuming: true },
writeStream: null,
hashedName: '29bafad3b32b11dc7ce934204952515ea5984b3c',
buffer: null,
sizeOfMessage: 0,
bytesRead: 0,
stubBuffer: null },
matchedCount: 1,
modifiedCount: 1,
upsertedId: null,
upsertedCount: 0 }
{
"ok": 1,
"nModified": 1,
"n": 1
}
{ _id: 'lala', a: 99, b: 20 }
the first object is the result returned from "updateOne()".
the second object is the result's "toString()" implementation and this is what's inside result.result (scroll back to top).
the last object is what I get after querying for the updated document.
you can find more examples on the native mongodb driver for nodejs website: http://mongodb.github.io/node-mongodb-native/2.2/api/Collection.html#updateOne
their are full of examples.